There have hitherto been known tire monitoring systems for acquiring information on tire conditions such as pressure, temperature, etc. of the atmosphere inside tire's air chamber.
As an exemplary technique of this type, systems for monitoring air pressure inside tire are disclosed in Japanese Patent Publication 2001-56263 (a first conventional example), Japanese Patent Publication 2000-182164 (a second conventional example), and so on.
The tire air pressure monitoring system of the first conventional example, provided in each tire of a vehicle, has a transmitter to transmit a tire air pressure signal for each tire outputted from an air pressure sensor, and multiple reception antennas extended to a neighborhood of each tire. The tire air pressure monitoring system includes a receiver to receive the tire air pressure signal from the transmitter, a display apparatus to inform the vehicle driver of air pressure condition of each tire, and a combining unit to output selectively the maximum voltage from among the voltages induced in each reception antenna. With this combining unit, the induction voltages of each reception antenna complement each other, and at the same time a selection is performed from among the receptions of each reception antenna. Thus the signal transmitted from the transmitter can be received in a stable manner.
Also, in the tire air pressure monitoring system of the second conventional example, a reception antenna is also provided within a receiver. Accordingly, the number of reception antennas extended to the vicinity of tire is reduced.
Meanwhile, an exemplary tire air pressure monitoring system in which reception antennas need not to be extended to a vicinity of tire is disclosed in Japanese Patent Publication 11-254926 (a third conventional example), Japanese Patent Publication 11-240315 (a fourth conventional example), and so on.
The third conventional example is a tire monitoring system which has a storage apparatus provided in an inner wall of tire within the air chamber of tire, and at the same time has a monitoring apparatus secured to a rim's inner wall face inside the air chamber of tire. In this system, the storage apparatus includes an antenna, a battery and an electronic chip; the monitoring apparatus includes a battery, an antenna, and a microchip connected to an amplifier. The battery of the monitoring apparatus is larger in capacity than that of the storage apparatus.
With the above described structure, in the system of the third conventional example, information on physical quantity within the tire's air chamber detected by the storage apparatus is transmitted by use of electromagnetic wave; the information is received by the monitoring apparatus. Also, the monitoring apparatus transmits the received information by use of electromagnetic wave having a larger output power than that of the storage apparatus. Accordingly, the power consumption of battery for the storage apparatus and monitoring apparatus can be reduced, thus enabling the continuous operation of the system without frequently exchanging the batteries.
In addition, in the third conventional example, the battery of the monitoring apparatus is separately disposed outside the tire's air chamber and connected to the monitoring apparatus via a connector provided by penetrating the rim, whereby the exchange of the battery of the monitoring apparatus is made easy.
In the fourth conventional example substantially similar to the third conventional example, information on physical quantity within the tire's air chamber detected by a tire tag is transmitted by use of electromagnetic wave; the information is received by a transponder. In addition, the transponder transmits the received information by use of electromagnetic wave having a larger output power than that of the tire tag. Accordingly, the power consumption of battery for the tire tag and transponder can be reduced, thus enabling the continuous operation of the system without frequently exchanging the batteries.
Patent document 1: Japanese Patent Publication 2001-56263Patent document 2: Japanese Patent Publication 2000-182164Patent document 3: Japanese Patent Publication 11-254926Patent document 4: Japanese Patent Publication 11-240315